Université de Fribourg

Direct and indirect effects based on changes-in-changes

Huber, Martin ; Schelker, Mark ; Strittmatter, Anthony

(Working Papers SES ; 508)

We propose a novel approach for causal mediation analysis based on changes-in- changes assumptions restricting unobserved heterogeneity over time. This allows disentangling the causal effect of a binary treatment on a continuous outcome into an indirect effect operating through a binary intermediate variable (called mediator) and a direct effect running via other causal mechanisms. We...

Université de Fribourg

An introduction to flexible methods for policy evaluation

Huber, Martin

(Working Papers SES ; 504)

This chapter covers different approaches to policy evaluation for assessing the causal effect of a treatment or intervention on an outcome of interest. As an introduction to causal inference, the discussion starts with the experimental evaluation of a randomized treatment. It then reviews evaluation methods based on selection on observables (assuming a quasi-random treatment given observed...

Université de Fribourg

Local Average Treatment Effects with or Without Defiers

Dahl, Christian M. ; Huber, Martin ; Mellace, Giovanni

In: Discussion papers on business and economics, 2017, vol. 2, p. 1-69

In heterogeneous treatment effect models with endogeneity, identification of the LATE typically relies on the availability of an exogenous instrument monotonically related to treatment participation. We demonstrate that a strictly weaker local monotonicity condition identifies the LATEs on compliers and on defiers. We propose simple estimators that are potentially more efficient than 2SLS,...

Université de Fribourg

Direct and indirect treatment effects - causal chains and mediation analysis with instrumental variables

Fröhlich, Markus ; Huber, Martin

In: Journal of the Royal Statistical Society Series B, 2017, vol. 79, no. 5, p. 1645-1666

The paper discusses the non‐parametric identification of causal direct and indirect effects of a binary treatment based on instrumental variables. We identify the indirect effect, which operates through a mediator (i.e. intermediate variable) that is situated on the causal path between the treatment and the outcome, as well as the unmediated direct effect of the treatment by using distinct...

Université de Fribourg

A simple test for the ignorability of non-compliance in experiments

Huber, Martin

In: Economics letters, 2013, vol. 120, no. 3, p. 389-391

This paper proposes a simple method for testing whether non-compliance in experiments is ignorable, i.e., not jointly related to the treatment and the outcome. The approach consists of (i) regressing the outcome variable on a constant, the treatment, the assignment indicator, and the treatment/assignment interaction and (ii) testing whether the coefficients on the latter two variables are...

Université de Fribourg

Sensitivity checks for the local average treatment effect

Huber, Martin Huber

In: Economics letters, 2014, vol. 123, no. 2, p. 220-223

The nonparametric identification of the local average treatment effect (LATE) hinges on the satisfaction of three instrumental variable assumptions: (1) Unconfounded assignment of the instrument, (2) no average direct effect of the instrument on the outcome within compliance types (exclusion restric- tion), and (3) weak monotonicity of the treatment in the instrument. While (1) often appears...

Université de Fribourg

Testing instrument validity for LATE identification based on inequality moment constraints

Huber, Martin ; Mellace, Giovanni

In: Review of economics and statistics, 2015, vol. 97, no. 2, p. 398-411

We derive testable implications of instrument validity in just identified treat- ment effect models with endogeneity and consider several tests. The identifying assump- tions of the local average treatment effect allow us to both point identify and bound the mean potential outcomes (i) of the always takers under treatment and (ii) of the never takers under non-treatment. The point identified...

Université de Fribourg

Testing the validity of the sibling sex ratio instrument

Huber, Martin

In: Labour, 2015, vol. 29, no. 1, p. 1-14

We test the validity of the sibling sex ratio instrument in Angrist and Evans (1998) using the methods proposed by Kitagawa (2008) and Huber and Mellace (2014). The sex ratio of the first two siblings is arguably randomly assigned and influences the probability of having a third child, which makes it a candidate instrument for fertility when estimating the effect of fertility on female labor...

Université de Fribourg

The Effect of Firms' Phased Retirement Policies on the Labor Market Outcomes of Their Employees

Huber, Martin ; Lechner, Michael ; Wunsch, Conny

In: ILR review, 2016, vol. 69, no. 5, p. 1216-1248

In this article, the authors assess the impact of firms’ offering a special form of phased retirement on their male employees’ labor market outcomes. The program aims at smoothing the transition from work to retirement and at decreasing costs in the public pension and unemployment insurance schemes through an increase in employment of elderly workers who otherwise would have exited...

Université de Fribourg

Direct and indirect effects based on difference-in-differences with an application to political preferences following the Vietnam draft lottery

Deuchert, Eva ; Huber, Martin ; Schelker, Mark

(Working Papers SES ; 473 (revised))

This paper proposes a difference-in-differences approach for disentangling a total treatment effect on some outcome into a direct effect as well as an indirect effect operating through a binary intermediate variable – or mediator – within strata defined upon how the mediator reacts to the treatment. Imposing random treatment assignment along with specific common trend (and further)...